The present invention relates to an apparatus for transferring or moving a plate-like sample, and more particularly to a sample transfer apparatus which loads and unloads the sample into and from a reaction chamber and a sample stage which is installed in the reaction chamber and is moved in the reaction chamber while holding the sample in a semiconductor relevant apparatus (such as an electron beam drafting apparatus, an electron microscope, a focused ion beam processing apparatus or the like) for treating the sample such as a semiconductor wafer, a glass substrate or the like.
A typical example of the sample transfer apparatus is explained in view of FIG. 1.
In a semiconductor manufacturing apparatus, the sample transfer apparatus used for transferring a semiconductor wafer, a glass substrate or the like determines a position where the sample is to be transferred in a three dimensional manner as shown in FIG. 1B. Namely, the height Z of the position where the sample is to be transferred is determined by a first drive shaft. Furthermore, using the center of the first rotary shaft of the sample transfer apparatus as the origin, the position where the sample is to be moved, a rotational angle "THgr" and a transfer distance R, and a direction xcex8 of the sample are determined by first, second and third rotating angles xcex81, xcex82, xcex83.
Here, a sample holding portion is requested to hold the sample without falling the sample during the transfer of the sample. To this end, as shown in FIG. 2, the sample holding portion is provided with a recess having a shape suitable for accommodating the sample and hence, even if the sample holding portion is slightly tilted, the sample is prevented from falling. Furthermore, the sample holding portion may be provided with a vacuum adhesion mechanism for fixedly mounting the sample to the sample holding portion.
Subsequently, an example of a typical two-axis sample stage is explained in view of FIG. 3.
In a semiconductor relevant apparatus, the two-axis sample stage used for holding the semiconductor wafer, the glass substrate or the like in the reaction chamber includes a first drive shaft and a second drive shaft which determine the position where the sample is to be transferred in a two dimensional manner. The sample is mounted on and held by a sample holding portion. The first drive shaft and the second drive shaft are respectively equipped with a first drive motor and a second drive motor and the sample is moved in X, Y directions by driving them respectively.
Here, the sample holding portion is requested to hold the sample without falling the sample as in the case of the sample transfer system and without moving the sample within the sample holding portion. Accordingly, as shown in FIG. 3, for example, the sample holding portion is provided with a recess having a shape suitable for accommodating the sample therein and hence, even if the sample holding portion is tilted, the sample is prevented from falling and shifting. Furthermore, as shown in FIG. 4, a method which uses a mechanism to clamp the sample mechanically or an static electricity chuck which adheres the sample using a static electric force for fixedly mounting the sample to the sample holding portion has been adopted.
Both the sample transfer apparatus and the sample stage which are used in a semiconductor relevant apparatus which processes the plate-like sample such as the semiconductor wafer or the glass substrate are provided with provisions for preventing the sample from falling.
However, in such a sample transfer apparatus, in case of the first method where the sample holding portion is provided with the recess having a shape suitable for accommodating the sample, it is necessary that the worked shape of the recess is produced with a high precision for firmly holding the sample. Accordingly, there exists the least margin or play between the shape of the sample and the shape of the recess and hence, depending on the position where the sample is placed, the sample is not accommodated in the recess and, as a result, the sample is transferred in an oblique condition and it gives rise to a problem that the sample falls. Furthermore, it is necessary to change the shape of the recess corresponding to the shape of the sample and its application method has been restricted. Furthermore, in case there is no affinity between the sample and the sample holding portion, a repulsive force works between them so that the sample cannot be accommodated in the recess.
Furthermore, in case of the second method which adopts the vacuum adhesion mechanism, it is an extremely effective method so long as it is used in the atmosphere. However, in the semiconductor manufacturing apparatus, it is often that the reaction chamber is under vacuum. In such a case, there exists no pressure difference between the sample holding side and its opposite side and hence, no sample holding force is generated and the method is totally inoperative.
Furthermore, with respect to the sample stage, in case of a mechanism which includes a presser foot for mechanically pressing the sample of the above-mentioned first method, since the sample cannot be pressed from its front surface, the sample must be pressed utilizing a force which is directed from the periphery to the center and hence, there arises a problem that the sample is deflected in an upwardly convex shape from the periphery to the center.
Still furthermore, in case of the static electricity chuck of the second method mentioned above, the sample 1 is adhered using the static electricity and hence, by finishing the surface of the sample flat, the sample is free from the deflection thereof which occurs in the above-mentioned first method. However, the method has several problems such that the static electricity chuck is made of ceramic and accordingly expensive, and has a complicated construction since a high voltage power source of some hundreds volts is necessary to generate the static electricity, and requires a careful designing for assuring the safety to avoid an electric shock accident since it uses the high voltage power source.
The present invention adopts a hydrogen bonding to overcome the above-mentioned problems.
Recently the research of the technology on the wafer lamination has been underway and it has been found that due to the hydrogen bonging which is attributed to the silicon oxide on the surface of the wafer, the wafers are laminated with each other. For instance, such a fact is introduced in xe2x80x9cSOI device viewxe2x80x9d (Applied Physics Vol.66, No. 11, 1997). In general, the hydrogen bonding is attributed to the nature of hydrogen present on the surface of the sample and it is known that the surface of a material to which the hydrogen bonding is applicable has hydrophilic property which prevents a repelling of water when it comes into contact with water. It is also known that in addition to the silicon oxide, silicon nitride can make use of the nature of the hydrogen bonding in the same manner.
The present invention makes use of the adhesion of sample using this hydrogen bonding and realizes a highly reliable holding of the sample.